VCU Torque test results

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Sucram said:
Ok just done a test as I've feeling a bit of tightness when parking up in the supermarket car park.

2001 Td4 Auto. Mileage 122,000 and from what I can see its the original VCU date stamp 00.

Today outside temp is around 6 deg. My Freelander hasn't been used for a couple of days.

Offside rear wheel jacked up, 1.2m ally spirit level with ratchet and 32mm socket strapped to one end. Weight is 9.4kg, (two old brake discs and a calliper). Timed through 45 deg came to 40 seconds.

I'm guessing that's to long and the VCU is stiffening up?
Click to expand...

Also I tried to turn the hub nut with my torque wrench. Started low at 40lb and ended up at 77lb before I could turn the wheel through 45deg with out the torque wrench clicking.

All test done on a cold day of around 4 deg. Temp. and Freelander not used for a few days since doing the last test above.

Prior to testing I don't get any skipping or scuffing of rear wheels, only a slight tightness or braking effect when parking up in the car park (thats forward with right hand lock), reversing on full lock into my drive seems ok, it can virtually pull its self in on tick over, only a couple of times have I had to touch the throttle. Hope I'm still ok to still drive it as it is until I can get a new VCU sorted?
 
I carried out the Turnip test Monday.
Ambient ground temperature was -1.2°C
Ambient VCU temperature was 1.6°C
Distance travelled was 12 miles.
Speed was mostly 30 to 50 mph with 2 miles at 70mph at the start of the journey.
The VCU temp at the end of the drive was 20.3°C
The rear diff was 38.6°C
The IRD was 68.1°C
I hope the results are relevant
 
Nodge68 said:
I carried out the Turnip test Monday.
Ambient ground temperature was -1.2°C
Ambient VCU temperature was 1.6°C
Distance travelled was 12 miles.
Speed was mostly 30 to 50 mph with 2 miles at 70mph at the start of the journey.
The VCU temp at the end of the drive was 20.3°C
The rear diff was 38.6°C
The IRD was 68.1°C
I hope the results are relevant
Click to expand...

Ok gave the VCU another temperature check this morning.
The ambient temp was 8.9°C
The VCU measured 28.6°C after the same journey as before.
I didn't have a chance to measure the diff or IRD.
 
sounds ok to me (what do I know?) - Bearing in mind the the VCU functions at <>100C, the temp yu are measing is quite low - but then again, i suppose that depends on whether the VCU is actually locking (I doubt it on the roads you mention) or the increase in temperature is just due to internal friction between the plates.

i would ask whether, if the fluid is not changing state, is an increase in temp from ambient to 28C a relistic thing to expect?

unfortunately, I dont think anyone here would know. It would be nice to have live data available for a drive under different conditions, so that temp fluctuations depending on circumstances could be measured. Pie in the sky methinks.
 
I would assume ( remember I also know nu-ting) the internal friction between plates and fluid would cause the temperature rise described.
There must always be some friction within the vcu, unless all the tyres are EXACTLY the same and therefore no difference in rotational speeds of the 2 parts of the prop shaft either side of the vcu.
Someone had mentioned on here before that its likely mismatched tyres cause premature degradation of the vcu fluid as its having to work harder due to constant increased frictio within the vcu. Sounds right to me....
who knows??
 
musky81 said:
I would assume ( remember I also know nu-ting) the internal friction between plates and fluid would cause the temperature rise described.
There must always be some friction within the vcu, unless all the tyres are EXACTLY the same and therefore no difference in rotational speeds of the 2 parts of the prop shaft either side of the vcu.
Someone had mentioned on here before that its likely mismatched tyres cause premature degradation of the vcu fluid as its having to work harder due to constant increased frictio within the vcu. Sounds right to me....
who knows??
Click to expand...

Even with perfectly matched tyres there would still be some stress on the VCU because of the reduced drive to the prop (R in IRD = Reduction).
Someone posted a good point some time ago (which corrected an false assumption I had!) that an improvement could be to modify the IRD so that the ratio was 1:1, then what you say would indeed be the case.
 
bukko said:
Even with perfectly matched tyres there would still be some stress on the VCU because of the reduced drive to the prop (R in IRD = Reduction).
Someone posted a good point some time ago (which corrected an false assumption I had!) that an improvement could be to modify the IRD so that the ratio was 1:1, then what you say would indeed be the case.
Click to expand...

a 1:1 ratio would make the vcu work harder surely. As it would engage the vcu, and drive to the rear, immediately.

or have i got that wrong?
 
Freelaner said:
a 1:1 ratio would make the vcu work harder surely. As it would engage the vcu, and drive to the rear, immediately.

or have i got that wrong?
Click to expand...

wrong way round , as idr drive isnt 50/50 ie equal speed front and back ,v/c is allways slipping even on a straight road ,more so the tighter the corner , the uneven split keeps some tension in system
 
jamesmartin said:
wrong way round , as idr drive isnt 50/50 ie equal speed front and back ,v/c is allways slipping even on a straight road ,more so the tighter the corner , the uneven split keeps some tension in system
Click to expand...

cheers JM ;)

it would be better to remove the prop if they were that way inclined.

then it would be a waste of time owning a 4x4 and a mundano would be a more sensible purchase :)
 
jamesmartin said:
there shouldnt be really ,once its well know v/cs are prone to stiffen with rate been dependant generally on its amount its slips ie poor tyre match theres no reason to check like other things to see if past best
Click to expand...

There isn't any fuss. It's called enthusiasm/interest/curiosity or whatever.
We all know these units fail, we all know why.
We don't know the actual facts and figures though. Some people claim to, but aren't sharing for business reasons. We have to take their word for it.
This isn't good enough for me though. I'm one of these wierdos who needs to know how and why. I'm not satisfied with being reliant on someone else who "knows what they are talking about".
This is why I am very interested when people post that they have recon'd their own VCU.
Although the results posted aren't particularly scientific, they are all we have and we can compare them with our own and others' experience, and learn from it.
 
Did another turnip test today. This was carried out after a 25 mile drive at 50 to 60 mph.
At the end of the run I measured the VCU at 35.9°C. Rear diff was 45.2°C.
Ambient temperature was 11°C
 
bukko said:
Even with perfectly matched tyres there would still be some stress on the VCU because of the reduced drive to the prop (R in IRD = Reduction).
Someone posted a good point some time ago (which corrected an false assumption I had!) that an improvement could be to modify the IRD so that the ratio was 1:1, then what you say would indeed be the case.
Click to expand...

Cheers, did more research on this, my something new learned for today :)
 
did my VCU check the other day, havnt got a way to test temperatures but car had been stood a few hours from doing 20 miles on motor way.

took 37s to do the 45degree rear wheel up..

she does feel tight in reverse on full lock though!!
 
I think I am the first person to have published the results on a brand new genuine vcu. 34 seconds.

for the one we took off the car (at 68k, 12 years) it was 46 seconds. Test to be done on cold car. At this reading you get a slightly worse reverse on full lock, though even on a brand new genuine one there appears to still be a slight presence.. only non-genuine ones are loose enough to completely lose this.

NEW: Freelander vcu viscous coupling test (freshly fitted genuine unit) - YouTube
OLD: https://www.youtube.com/watch?v=8j_ERzLbdi8

Kind regards

James
 
Would be good if you could keep doing the tests on the new vcu to see if it loosens up a little in use, or if it stays the same for an extended period of time.

I think that it would add data of real worth to this thread. It would also give us all a real bench mark of the way a new vcu behaves over time.
 
Did another turnip test today.
After 20 miles with speeds ranging from 40 to 70.
VCU measured 37°C
Ambient temperature was 9°C
Now for something curious!
The front propshaft measured 55°C at the UJ where it's splined to the VCU.
The rear propshaft measured 51°C at its UJ splined to the VCU.
So being that the VCU is mechanically connected to the propshafts, there must be a heating effect on the VCU!!
 
jtq4u said:
I think I am the first person to have published the results on a brand new genuine vcu. 34 seconds.

for the one we took off the car (at 68k, 12 years) it was 46 seconds. Test to be done on cold car. At this reading you get a slightly worse reverse on full lock, though even on a brand new genuine one there appears to still be a slight presence.. only non-genuine ones are loose enough to completely lose this.

NEW: Freelander vcu viscous coupling test (freshly fitted genuine unit) - YouTube
OLD: https://www.youtube.com/watch?v=8j_ERzLbdi8

Kind regards

James
Click to expand...

If you can, can you do a test after a nice 15-20 mile+ journey while it is warmed up fully? Ta!! :cool:
 
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